1. Field of the Invention
This invention relates to the manufacture of methylene bis(methyl anthranilate).
2. Description of the Prior Art
Methylene bis(methyl anthranilate) has been found useful as an amine-type curing agent in a number of applications such as in curing epoxy resins or as a chain-extender in urethane formulations. The compound is most often prepared by reacting formaldehyde with methylanthranilate in the presence of acetic acid to produce an intermediate product. The acetic acid is then removed by either distillation or neutralization and HCl is then added to rearrange the intermediate to obtain the methylene bis(methyl anthranilate). Again the hydrochloric acid has to be removed by neutralization.
The disadvantages of employing the just described scheme are obvious. In the first place there are handling drawbacks as well as safety considerations involved in the use of the two liquid acids. Secondly, the acids must necessarily be neutralized leading to unwanted salt production, which salt must necessarily be disposed of in an environmentally safe manner. Again, one must resort to relatively expensive corrosion resistant equipment, particularly when employing a strong acid such as hydrochloric acid. Lastly, as just described the overall process is multi-step in nature adding to the overall expense.
It would therefore be a distinct advance in the art if methylene bis(methyl anthranilate) could be made in an efficient, one-step process without necessary resort to use of corrosive acids which must be subsequently neutralized in order to properly isolate the desired product. Other objects will appear hereinafter.